Russian luxury case company Caviar, known for creating extravagant and flamboyant replacement casings for Apple’s iPhone, has launched its latest custom creation.

The company on Wednesday announced its specially customized iPhone XS models that come with a built-in mechanical skeleton watch.

The Grand Complications Skeleton collection features iPhone XS and XS Max models in pink gold, titanium and black and gold. All models feature mechanical watch components built right in the phone’s casing.

According to Mac Rumors, the front of the customized iPhones is as it is but the back features a mechanical clock with accurate Swiss watch mechanism, and showcases guilloche work and engravings.

Caviar said that the watch it built into the custom iPhones is wound manually through a crown placed on the right side of the casing.

The company said that the collection is inspired by luxury watches. It added that it decided to “complicate” the smartphone with a mechanical watch and hinted of plans to continue the series with improvements inspired by the world of watches.

“The passage of time, majestic and implacable is still worth watching by real hands. The watch is, if we may say so, the beginning of the progress, the mechanism, from which everything has begun,” a representative of the company said in a press release.

The price of Caviar’s custom iPhones are several times more expensive than the regular iPhone XS. The cheapest of theGrand Complications Skeleton collection is the titanium iPhone XS model that costs $6,320.

The Black and Gold model is the most expensive at $8,080. It features a body decorated with engraved blackened titanium and engraved decorative gears in gold covering.

“Now you have at your disposal not only a modern smartphone that has nothing impossible in the technological area, but also a precise skeleton watch that glamorously complement the grandiose panel of decorative gears covered with gold on the back side of the body,” Caviar described the Grand Complications Skeleton Black & Gold.

Only 99 units for each design are being sold by the company. The limited number is likely due to the high cost and the difficulty in making them.

Earlier this year, Caviar also released the iPhone X Tesla. The customized iPhone X is plated in carbon and gold and comes with a built-in solar battery. The device, which costs more than $4,000, is named after Elon Musk’s company with ties to sustainable energy. The iPhone X Tesla is the first of Caviar’s devices with its own solar battery.